1. Nucleic Acids
“Informational Polymers”: Code for all of the proteins in an organism
Polymer: Nucleic Acid
Monomers: Nucleotides
Each Nucleotide is made up of:
1) Phosphate Group
2) Pentose 5-C Sugar
Ribose or deoxyribose
3) Nitrogenous bases
Adenine (A), Cytosine(C), Thymine (T), Guanine(G), and Uracil (U)

2. Nucleic Acids Polymers
DNA
RNA (tRNA, mRNA, rRNA)
The nitrogenous bases (A, C, G, T) are what makes up the DNA “code”
RNA codes are transcribed or made from DNA codes
Proteins are then translated or made from RNA codes

3. Central Dogma of Molecular Biology!
Scientists call this the:
DNA
DNA
Central Dogma of Molecular Biology!
RNA
RNA
Protein
Protein

4. How do we know that all of our genetic information comes from DNA
How do we know that all of our genetic information comes from DNA? (instead of protein)
What type of experiment would you design to determine that DNA is the source of all genetic information?

5. The smooth colonies must carry the disease!
Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation
Frederick Griffiths was a bacteriologist studying pneumonia
He discovered two types of bacteria:
Smooth colonies
Rough colonies
CONCLUSION:
The smooth colonies must carry the disease!

6. Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation
When heat was applied to the deadly smooth type…
And injected into a mouse…
The mouse lived!

7. Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation
Griffith injected the heat-killed type and the non-deadly rough type of bacteria.
The bacteria “transformed” itself from the heated non-deadly type to the deadly type.

8. Griffith’s Experiment did not prove that DNA was responsible for transformation
How would you design an experiment to prove that DNA was responsible for transformation?

9. Avery, McCarty, and MacLeod Repeated Griffith’s Experiment
Oswald Avery
Maclyn McCarty
Colin MacLeod

10. To the Heat-Killed Smooth Type, they added enzymes that destroyed…
They then added Heat-Killed Smooth to the non-deadly Rough Type of Bacteria
To the Heat-Killed Smooth Type, they added enzymes that destroyed…
Carbohydrates
Lipids
Proteins
RNA
DNA

11. DNA was the transforming factor!
S-Type Carbohydrates Destroyed
S-Type Lipids Destroyed
S-Type Proteins Destroyed
S-Type RNA Destroyed
S-Type DNA Destroyed
Conclusion:
DNA was the transforming factor!

12. The Hershey-Chase Experiment
Protein coat
Alfred Hershey & Martha Chase worked with a bacteriophage:
A virus that invades bacteria. It consists of a DNA core and a protein coat
DNA
movie

13. Protein coats of bacteriophages labeled with Sulfur-35
Hershey and Chase mixed the radioactively-labeled viruses with the bacteria
Bacterium
Phage
The viruses infect the bacterial cells.
Bacterium
DNA of bacteriophages labeled with Phosphorus-32

14. Protein coats of bacteriophages labeled with Sulfur-35
Separated the viruses from the bacteria by agitating the virus-bacteria mixture in a blender
DNA of bacteriophages labeled with Phosphorus-32

15. Protein coats of bacteriophages labeled with Sulfur-35
Centrifuged the mixture so that the bacteria would form a pellet at the bottom of the test tube
Measured the radioactivity in the pellet and in the liquid
DNA of bacteriophages labeled with Phosphorus-32

16. DNA carries the genetic code!
The Hershey-Chase results reinforced the Avery, McCarty, and MacLeod conclusion:
DNA carries the genetic code!
However, there were still important details to uncover…

17. But first, Review -- What are the monomers of DNA?
Composed of repeating nucleotides containing:
Deoxyribose 5-Carbon sugar
Phosphate group
Nitrogen base: (4 kinds)
Adenine (A) Thymine (T)
Cytosine (C) Guanine (G)

18. The Race to Discover DNA’s Structure

19. The Race to Discover DNA’s Structure
In the 1940’s, Linus Pauling discovered the alpha-helical structure of proteins.

20. Stop here to discuss conclusion to Chargaff’s Inquiry Activity

21. The Race to Discover DNA’s Structure
Why do you think the bases match up this way?
Adenine + Guanine = Too wide
1950
Chargaff’s Rule: Equal amounts of Adenine and Thymine, and equal amounts of Guanine and Cytosine
Thymine + Cytosine = Too Narrow
Erwin Chargaff
Adenine + Thymine Perfect Fit Cytosine + Guanine

22. The Race to Discover DNA’s Structure
X-Ray diffraction image of DNA taken by Franklin in 1951
Maurice Wilkins
Rosalind Franklin

23. The Race to Discover DNA’s Structure
1953
Compiled data from previous scientists to build a double-helical model of DNA
James Watson
Francis Crick

24. The Race to Discover DNA’s Structure was Over
Purines
Pyrimidines
The Race to Discover DNA’s Structure was Over
DNA is made up of :
Four nitrogenous bases: Adenine, Thymine, Guanine and Cytosine
These follow the rules of base-pairing
Purines bond with Pyrimidines:
Adenine bonds with Thymine
Guanine bonds with Cytosine
A sugar-phosphate backbone
A sugar-phosphate backbone plus one nitrogenous base is called a nucleotide.
DNA is arranged in a double-helix, made up of nucleotide monomers.

25. DNA Overview P S a. Double helix c. One pair of bases O C purine base
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P S
a. Double helix
c. One pair of bases O C
purine base
pyrimidine base
phosphate
3' end
5' end 5' 1' 3' 2' 4'
deoxyribose
b. Ladder structure